In known manner, a motor vehicle suspension system includes a McPherson strut supporting a vehicle axle and wheel. A suspension thrust bearing is disposed in the upper part of the McPherson strut, at the end opposite the wheel and the ground, between a suspension spring and an upper member rigidly fastened to the body of the vehicle. The spring is disposed around a shock absorber piston rod, the end of which may be rigidly fastened to the body of the vehicle. The suspension thrust bearing includes at least one bearing, with an upper race rigidly fastened to the upper member and a lower race on which the spring comes to bear axially, either directly or indirectly.
Accordingly, the suspension thrust bearing enables axial forces to be transmitted between the suspension spring and the body of the vehicle, whilst allowing relative angular movement between the races of the bearing. This relative angular movement be the result of compression of the suspension spring and/or of turning of the steerable wheels. Known devices enable rotation of the complete suspension and the steerable wheel when a driver of the vehicle turns the steering wheel. On the other hand, as the shock absorber piston rod is fixed relative to the body of the vehicle, a resisting torque is generated between the rod and the shock absorber body.
To reduce the resisting torque it is known to add a second bearing to the suspension thrust bearing, between the shock absorber piston rod and the upper member fixed to the body. This increases its cost and its overall size, however.
US-A-2007 144 850 describes such a suspension thrust bearing with two bearings.
Alternatively, there is known a suspension thrust bearing comprising a single bearing combining the two functions, on the one hand rotation of the suspension and on the other hand reduction of the resisting torque of the shock absorber piston rod. In addition to these two functions, the thrust bearing and its bearing must be adapted to support high loads and vibrations.
US-A-2007 144 850 also describes, by way of prior art, such a suspension thrust bearing with only one bearing. The shock absorber piston rod is fixed to the upper race of the bearing, whilst the suspension spring bears axially on a cup that is centred on the lower race of the bearing. This lower race has complex shapes, is bulky and is not a pressing. Such a suspension thrust bearing is not entirely satisfactory, in particular in terms of behaviour in the face of loads and vibrations.
Moreover, for some particular applications it is advantageous to be able to fix the shock absorber piston rod to the lower part of the suspension thrust bearing, on which the suspension spring bears.
The object of the present invention is to propose an improved suspension thrust bearing device.